Copy Word to Struct - TIA Portal

[ASF]

Hi all,

Straight up question: I'm using TIA Portal and an S7-1200, and wanting to do a straight bitwise copy of all the data in a Word to put it into a Struct (which consists of a byte and 8 bools). Is there a way to do this? I've tried all the instructions that I can think of, but they all give me data type mismatches.

Context (in case there's a better way to approach what I'm doing): I'm getting a 16-bit integer coming in from a Modbus TCP device, and this particular status word contains:
- Bit 0-7: Value 1
- Bit 8-12: Value 2
- Bits 13, 14 and 15: status bits
I can bring it straight into a Struct tag of one byte and 8 bools, but then I have no easy way of re-assembling the value from Bits 8-12 back into a meaningful value. So I decided to bring it into an Int. Then I can use AND's and bit shift instructions to extract Value 1 and Value 2, and all I have to do then is extract the Bool's.

I can think of two ways to do this:

1. Address the bit within the Int: e.g. just use %DB331.DBX2.13 to turn on a coil. That coil becomes my bool. This works, but gives me IEC warnings

2. Move the Int into an M word (e.g. MW100) and then address (e.g.) M100.5 to get my Bool. Which also works

And while they both work, I'm thinking it would still be much simpler if I could just do a straight copy. Is it possible, or should I just pick one of my two options above and move on?

Thanks!

 

[ASF]

I've just worked out that I can use a MOVE instruction if I specify the word in the DB by it's offset, rather than it's name (MOVE DB331.DBW6 to DB331.DBW18), but again, I get an IEC warning. So if there's a more elegant solution I'm eager to hear it

 

[mk42]

As far as I know, Siemens doesn't have any 5 bit data types, so your structure couldn't match up exactly. I don't think a straight copy is possible.

One other way to address the values within the tag in the 1200 is to use what they call "slice" addressing. If you address the memory location by name, you can append ".B0" to mean the least significant byte, ".X3" to grab the 4th bit (counting from 0), etc. So you could copy out the first value from "Datablock.tagname.B0", to do it symbolically, and not have to deal with the offsets. You could use .X15, or possibly .B1.X7 to grab one of the status bits at the end.

The above might avoid the IEC error, but you still have the same issues with the 5 byte value. In the end, you still have to do something like one of the ideas you already had.

 

[ASF]

Thanks for the response. I'm currently using the ".X3" to grab the bool's individually (DB331.DBX1.3), and it works, but still gives me the IEC error.

As far as the five bit data type, that's not an issue - I just get the whole Int and run it through an AND and a Bit Shift, and store it in another Int. Now I just want to try and grab the bool's - preferably without generating an IEC error

 

[rQx]

You seem to have in a non optimized DB, if you move your incomoing value to a DB with optimized settings you can use bitslicing without error. Example:

Move your value to DB10 and name it MODBUS

Then just adress it MODBUS.X0 to access the first bit.
MODBUS.B0 for first byte
MODBUS.W0 for first word.

https://support.industry.siemens.com/cs/#document/57374718?lc=en-WW

 

[ASF]

Aha, that works nicely!

Just to dot the i's and cross the t's, the addressing format is:

[DB Name].[Element Name].x[Bit Number]

e.g. Weight_TX_Data.Status_Word.x13 where Weight_TX_Data is the DB, Status_Word is a Word tag in the DB, and I'm addressing bit 13 of Status_Word.

Thanks!

 

[rQx]

Yes, that's correct! The optimized datablocks are overall better to use so try to use optimized rather then the non optimized. Sometimes you must use the non-optimized for communication etc as you might know

 

[Jeebs]

But what if one wants to do:
Weight_TX_Data.Status_Word.Enabled
In stead of:
Weight_TX_Data.Status_Word.X13

 

[rQx]

How do you mean? What is "enabled", I know the word but what do you want to do?

 

[Jeebs]

Give .X13 a symbolic name and use it by its symbolic name.

 

[rQx]

Ah, I don't think you can do that since we only "slice" the word into bits in the ladder. The bits we access isn't specified anywhere in any DB. At least as far as I know.

 

[Manglemender]

I haven't used TIA portal much but does it not support UDTs?

The conventional way to handle this would be to create a UDT with the structure that corresponds to the slave data and then transfer said data into an instance of the UDT.

Nick

 

[ASF]

Jeebs, what rQx said is correct - the Status tag is an Int, so I can't give each bit a symbolic name. I could make it a STRUCT tag with individual bools, and do that, but then I'm back to my previous problem of getting 5 Bool's packed back into an Int (see original post)

Manglemender - yes, I could create a UDT, but then I'm still stuck in the same place - how do I get my data into it? The biggest problem here was not that I need to extract 16 bits out of an Int - if it were 16 individual bits, I'd have just created a Struct tag with 16 bools, brought the data straight into there, and I'd already be at the pub. The problem is because I have 16 bits of information where the first 8 bits are to be read as a decimal value, the next 5 bits are to be read as a decimal value, and then the next three bits are to be read as individual bools. As mk42 said, there's no 5-bit data type in Siemens, so I can't create a UDT to fit them all into the right place.

In any case, with the information in posts 5-7, I've got what I needed. Thanks everyone!

 

[wimpiesplc]

can't you use library function BLKMOV (SFC20) ?

 

[BryanG]

I was thinking POKE_BLK, it doesn't care about data types, but I don't know if it would be acceptable under IEC'what do you call it'.